The present invention relates to a clamping apparatus for clamping elongated members to be clamped such as pipes so that an angle between the members to be clamped can be freely adjusted.
A clamping apparatus of this type is used to clamp a pipe for forming a scaffold at a construction site or to set various musical instruments such as tom-toms, a cow bell and an electronic drum set on a musical instrument stand. For example, in order to clamp two pipes in a substantially parallel relationship with respect to each other, an apparatus having an arrangement as shown in FIG. 5 is generally used. That is, a clamping apparatus 1 comprises an elongated base plate 2, and a pair of left and right press plates 4 and 5 opposing the surface of the base plate 2 via members to be clamped 3A and 3B, respectively. The press plate 4 (5) is urged against the member to be clamped 3A (3B) by an urging means comprising bolts 6A and 7A (6B and 7B) and a nut 8 (9), thereby clamping the member to be clamped 3A (3B) between the base plate 2 and the press plate 4 (5). A pair of left and right holding grooves 10 and 11 are formed in the surface of the base plate 2, i.e., the surface opposing the press plates 4 and 5 in a direction perpendicular to the longitudinal direction of the plate 2. The members to be clamped 3A and 3B abut against the grooves 10 and 11, respectively, thereby preventing a positional deviation thereof. Similarly, holding grooves 12 and 13 for positioning the members to be clamped 3A and 3B are formed in central portions of the inner surfaces of the press plates 4 and 5, respectively. Notched holes 14A and 14B are formed at the outer ends of the press plates 4 and 5, respectively. The inner ends of the press plates 4 and 5 are pivotally connected to the proximal end portions of the bolts 6A and 6B by connecting pins 15, respectively. The distal end portions of the bolts 6A and 6B are inserted in insertion holes 16 formed in central portions of the base plate 2. Nuts 8 are threadably engaged with projecting ends of the bolts 6A and 6B. The proximal end portions of the bolts 7A and 7B are inserted in notched recesses 19A and 19B formed in both end faces of the base plate 2, respectively, and pivotally connected thereto by shaft pins 20. The T nut 9 is threadably engaged with the distal end portion of the bolt 7A (7B) and screwed in the notched hole 14A (14B) of the press plate 4 (5) upon clamping of the member to be clamped 3A (3B), thereby locking the outer end of the press plate 4 (5). By tightening the T nuts 9, the press plates 4 and 5 are urged against the members to be clamped 3A and 3B, respectively.
For example, one of the members to be clamped 3A and 3B is a pipe of a musical instrument stand, and the other one is a holder of a musical instrument to be mounted on the stand.
Reference numerals 21 denote compression coil springs for preventing looseness of the nuts 9.
The conventional clamping apparatus 1 having the above arrangement, however, is for clamping the members to be clamped 3A and 3B in a substantially parallel relationship with respect to each other. That is, a clamping angle between the members to be clamped cannot be changed. Therefore, in order to clamp the members to be clamped at a right angle, a clamping apparatus having a shape suitable for this purpose must be used. As a result, since the number of types of the clamping apparatuses 1 is increased, manufacture and management of the apparatuses become troublesome. For this reason, a clamping apparatus, in which base plates of two tightening tools are connected by a bent connecting rod having a predetermined length so that an angle between the two tightening tool can be freely adjusted, has been developed. In this clamping apparatus, however, since the connecting rod tends to be elongated because screws are used to connect the base plates to the connecting rod, a distance between members to be clamped cannot be shortened. In addition, the manufacturing cost of this apparatus is undesirably high.